Our sash window installation guide offers clear, step-by-step instructions to ensure a precise and long-lasting fit.
Sash Window Measuring and Installation Guide
Measure right. Fit right.
This guide shows how to take accurate sizes and how to fit new timber sash windows. It covers opening checks, three‑point measurements, diagonals, depth and cill notes, then moves into dry‑fitting, fixing, packing, sealing, traditional pointing, and final checks.
Who this measuring guide is for
Builders and site carpenters
Homeowners managing supply‑only installs
Conservation area projects (check local rules)
What you’ll need (survey)
5–8 m tape, laser measure (optional), spirit level
Square, notebook or survey sheet
Straightedge, small pry bar to lift trims if needed
Phone/camera for photos
Download Measuring Guide (PDF)
Get concise measuring steps: 3‑point widths/heights, diagonals, depth checks and the tolerance to allow—so you can submit accurate order sizes first time.
Download Installation Guide (PDF)
Tools and materials (install)
Levels, drill/driver, fixings, packers/shims
Low‑expansion foam, backer rod
Hybrid polymer/LMN sealant, paintable caulk
PPE and protection materials
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